The present invention generally relates to methods and apparatus for sealing vascular punctures and wounds, and more particularly, to a device that may be used to deliver ultrasound energy to a vascular puncture site to arrest bleeding.
Various surgical procedures are performed by medical specialists such as cardiologists and radiologists, utilizing percutaneous entry into a blood vessel. To facilitate cardiovascular procedures, a small gauge needle is introduced through the skin and into a target blood vessel, often the femoral artery. The needle forms a puncture through the blood vessel wall at the distal end of a tract that extends through the overlying tissue. A guide wire is then introduced through the bore of the needle, and the needle is withdrawn over the guide wire. An introducer sheath is next advanced over the guide wire; the sheath and guide wire are left in place to provide access during subsequent procedure(s). The sheath facilitates passage of a variety of diagnostic and therapeutic instruments and devices into the vessel and its tributaries. Illustrative diagnostic procedures include angiography, intravascular ultrasonic imaging, and the like; exemplary interventional procedures include angioplasty, atherectomy, stent and graft placement, embolization, and the like. After this procedure is completed, the catheters, guide wire, and introducer sheath are removed, and it is necessary to close the vascular puncture to provide hemostasis and allow healing.
The most common technique for achieving hemostasis is to apply hard pressure on the patient""s skin in the region of the tissue tract and vascular puncture to form a blood clot. Initially, pressure is applied manually and subsequently is maintained through the use of mechanical clamps and other pressure-applying devices. While effective in most cases, the application of external pressure to the patient""s skin presents a number of disadvantages. When applied manually, the procedure is time-consuming and requires the presence of a medical professional for thirty minutes or more. For both manual and mechanical pressure application, the procedure is uncomfortable for the patient and frequently requires the administration of analgesics to be tolerable. Moreover, the application of excessive pressure can occlude the underlying artery, resulting in ischemia and/or thrombosis. Even after hemostasis has apparently been achieved, the patient must remain immobile and under observation for hours to prevent dislodgment of the clot and to assure that bleeding from the puncture wound does not resume. Renewed bleeding through the tissue tract is not uncommon and can result in hematoma, pseudoaneurisms, and arteriovenous fistulas. Such complications may require blood transfusion, surgical intervention, or other corrective procedures. The risk of these complications increases with the use of larger sheath sizes, which are frequently necessary in interventional procedures, and when the patient is anticoagulated with heparin or other drugs.
In recent years, several hemostasis techniques have been proposed to address the problem of sealing vessel wall punctures following percutaneous transcatheter procedures. Related prior art is described in U.S. Pat. Nos. 5,320,639; 5,370,660; 5,437,631; 5,591,205; 5,830,130; 5,868,778; 5,948,425; 6,017,359; and 6,090,130. In each of these patents, bioabsorbable, thrombogenic plugs comprising collagen and other materials are placed proximal to the vessel wall puncture site to stop bleeding. The large hemostasis plug stimulates blood coagulation in the vessel puncture site, but blocks the catheter entry tract, making catheter reentry more difficult, if required.
Other related prior art disclosed in U.S. Pat. Nos. 5,707,393; 5,810,884; 5,649,959; and 5,350,399 provides for the use of small dissolvable disks or anchors that are placed in the vessel to block or clamp the puncture hole. However, any device remaining in the vessel lumen increases the risk of thrombus formation. Such a device also can detach and cause occlusion in a distal blood vessel, which would likely require major surgery to remove.
Additional prior art includes U.S. Pat. Nos. 5,779,719; 5,496,332; 5,810,850; and 5,868,762. In the disclosure of these patents, needles and sutures delivered through catheters are used to ligate the puncture. The suturing procedure requires particular skill. Suture material left in the vessel may cause tissue irritation that will prolong the healing process.
Still other prior art is disclosed in U.S. Pat. No. 5,626,601, wherein a procoagulant is injected into the puncture, with a balloon catheter blocking inside the vessel lumen. However, in some cases, the clotting agent may leak past the balloon into the vessel lumen and cause stenosis.
Yet other prior art references related to this topic include U.S. Pat. Nos. 4,929,246; 5,810,810; and 5,415,657, which disclose the use of a laser or of radio-frequency (RF) energy that is transmitted to the blood vessel through a catheter to thermally fuse or weld the punctured tissue together.
All of the above cited prior art references require either introducing and leaving foreign objects in the patient""s body, and/or inserting a tubular probe of large diameter into the tissue channel left by the catheter in order to seal the puncture.
As will be evident from the preceding discussion, there is a clear need for an improved method and apparatus for sealing a puncture left in a blood vessel, following an intravascular catheterization procedure. The method and apparatus should cause rapid cessation of bleeding, not rely on blood clot formation, and should be independent of the patient""s coagulation status. By employing such a method and apparatus, the patient will be more comfortable as a result of shortened hemostasis and ambulation times, and physician and hospital resources will thereby be minimized. In addition, the method and apparatus should not leave any foreign object in the patient""s body, to reduce the risk of stenosis at or distal to the puncture wound. An ideal device will be noninvasive and should not include any component that must be inserted in the catheter tract and which might further damage the wound and impede the sealing process.
In accord with the present invention, a method and apparatus are defined that provide advantageous solutions to the problem of expeditiously and safely sealing vascular catheter entry wounds made in connection with medical procedures. The method includes the steps of determining a site of the puncture in the vascular vessel and positioning an ultrasonic transducer applicator at a position adjacent to the site. The ultrasonic transducer applicator is coupled to a control that includes a processor programmed to administer ultrasonic energy in a manner that efficaciously seals a puncture. A user is enabled to initiate a process that is controlled by the control, so that very little operator training is required. The control automatically controls the ultrasonic transducer applicator so that the ultrasonic energy produced by the ultrasonic transducer applicator is focused at the site and is administered at a sufficient intensity and duration to denature tissue at the puncture, closing and sealing the puncture.
To determine the site of the puncture, an imaging ultrasonic beam is generated with the ultrasonic transducer applicator and is transmitted into the patient, proximate an expected location for the site. A reflection of the imaging ultrasonic beam is then received from within the patient using the ultrasonic transducer applicator, producing a corresponding output signal. The output signal is processed with the processor included in the control to facilitate determining the site of the puncture.
For example, a visual indication of a location of the site of the puncture can be provided to enable an operator to position the ultrasonic transducer applicator so that the ultrasonic energy produced by the ultrasonic transducer applicator is directed at the site. Such a visual indication may be in the form of, for example, lighted display indicators. In one form of the present invention, the visual indication includes an image of the site in which an axis of the vascular vessel is visually evident, enabling the operator to position the ultrasonic transducer applicator longitudinally along the axis of the vascular vessel so that the ultrasonic energy is directed at the site of the puncture.
In an alternative embodiment, an object is provided that extends into the puncture from outside the patient. The operator can then estimate the location of the puncture along the longitudinal axis of the vessel based upon a disposition of the object extending outside the patient. As yet a further alternative, the visual indication includes an image of the site in which the object extending into the puncture is evident. An estimate is made of the location of the puncture based upon a disposition of the object in the image.
Finally, the output signal can be processed with the processor to determine the site of the puncture. An indicator disposed on the ultrasonic transducer applicator can be controlled by the processor to provide an indication of a direction in which the ultrasonic transducer applicator should be moved to position it adjacent to the site of the puncture.
The processor is preferably used for automatically controlling at least one of a direction, an intensity, and a focus of the ultrasonic energy, to ensure that the ultrasonic energy is administered to the site of the puncture. Using the processor, the ultrasonic energy is directed so as to overscan the site of the puncture, ensuring that the puncture is closed and sealed. For example, the processor can move the focus of the ultrasonic energy while it is being administered, to overscan the site of the puncture. As another alternative, an ultrasound emitter of the ultrasonic transducer applicator has an aspheric shape so that the ultrasonic energy that is directed at the site of the puncture covers a larger area that overscans the site. Other transducer configurations that provide a laterally broadened focal region may also be employed.
Preferably, the ultrasonic transducer applicator uses a common array of transducers for generating both the imaging ultrasound beam and the ultrasound energy that closes and seals the puncture.
It is also contemplated that the administration of the ultrasonic energy be interrupted, to again generate the imaging ultrasound beam, thereby confirming whether the ultrasonic energy is being directed at the site of the puncture.
The processor is preferably employed to control a force applied against a surface of the patient using a force generator included in the ultrasonic transducer applicator. This force is controlled so that a pressure developed by the force is sufficient to substantially stop fluid leakage from the vascular vessel, but not so great as to substantially occlude fluid flow through the vascular vessel.
Another aspect of the invention is directed to enclosing the unit applicator within a protective, acoustic coupling shell. The protective, acoustic coupling shell is adapted to contact an external dermal portion of the patient in order to convey the ultrasonic energy transdermally to the site of the puncture, while isolating an ultrasonic emitter surface on the ultrasonic transducer from direct, contacting exposure to the patient. The protective, acoustic coupling shell is preferably pre-sterilized and preferably includes a gel patch on an outer surface that is protected by a tab. The tab is removed prior to contacting the external dermal surface of the patient.
Still another aspect of the present invention is directed to apparatus. The apparatus include elements that carry out functions generally consistent with the steps of the method discussed above.